Fix odd shadowing bug in XL init. (#3874)

Fixes #3873

Makefile

@@ -71,10 +71,8 @@ verifiers: vet fmt lint cyclo spelling
 
 vet:
 	@echo "Running $@:"
-	@go tool vet -all ./cmd
+	@go vet github.com/minio/minio/cmd/...
-	@go tool vet -all ./pkg
+	@go vet github.com/minio/minio/pkg/...
-	@go tool vet -shadow=true ./cmd
-	@go tool vet -shadow=true ./pkg
 
 fmt:
 	@echo "Running $@:"

cmd/xl-v1.go

@@ -140,9 +140,9 @@ func newXLObjects(storageDisks []StorageAPI) (ObjectLayer, error) {
 	// Check if object cache is enabled.
 	if xl.objCacheEnabled {
 		// Initialize object cache.
-		objCache, err := objcache.New(maxCacheSize, objcache.DefaultExpiry)
+		objCache, oerr := objcache.New(maxCacheSize, objcache.DefaultExpiry)
-		if err != nil {
+		if oerr != nil {
-			return nil, err
+			return nil, oerr
 		}
 		objCache.OnEviction = func(key string) {
 			debug.FreeOSMemory()